loose crank bolt...

Have any of you guys ever had a problem with the crank bolt backing out? What have you done to remedy the problem? Also what is the thread size of the bolt? 7/16-20? Yesterday as I was taking my car out for a spin my crank bolt backed out causing me to shear a crank key. Any help would be greatly appreciated.

Hi I use a wheel stud to hold the hub on
(some simlar to the way head studs work)
It works great and has not back out ......

Use red loctite. It is good stuff.

Just a warning...

The red Loctite is known as stud & bearing mount. It usually requires high heat (enough to warp the crank) to remove fasteners installed with this..... not something to do with a crankshaft unless you plan to get it cut/straightened before you re-use it.

Properly torqued, the bolt should not come loose. Generally the key shears first, then the bolt backs out due to rotation. With supercharged cars, you should measure the press fit between the crank/hub to be sure it is tight enough (to prevent shearing the key under high boost.

The press fit & the key should handle the load. If the bolt was meant to do this, it would have left hand threads to prevent loosening.

i actually broke that bolt in 2 peices pulling the hub on with the bolt. Guess i stretched the threads, b/c i welded to it and it still wouldnt turn at all. So i just used lots of red locktight, smeared it all over the hub, and hammered it on. Been like that for awhile now and hasnt budged a bit. Im pretty convinced if i ever need to get it off again, i will be using a cutting torch

Thanks for the advice guys.

Maldo:

Where did you pick up the stud and how long is it?


Lonnie:

What do you recommend I torque the crank bolt to? Also do you recommend using a different type of loctite. I really don't want to mess with putting a torch on the crank.

Thanks again. :)

I have the same problem. What a PITA. I've used blue locktite but it still backs off. I've just been checking it about twice a month to make sure its good.

I had a friend DESTROY his crank because he never checked the bolt. It backed off and ended up costing him an engine.:eek:

I have never had a bolt back out using red loctite. I use it on anything I have that needs it. And I do not have to use heat to break the bolt loose.

If the bolt is torqued down correctly it should not come out. The bolt may be worn out. The crank hub bolt on an LS1 is a use once bolt. Every time you take the bolt out, it needs to be replaced. So maybe you need a new bolt.

I'll give this a shot.

I use the loctite 243 which is med strength "blue" for this type of fastening & never had a problem.

The "red" is not an accurate description.

For permanent fastening under 3/4" bolts the "red" is Loctite 262. It states to use heat (262C approx. 500F) to remove or a risk of bolt breakage/thread damage can occur.

"Red" stud/bearing mount is Loctite 270/272. This is essentially permanent & will require excessive heat to remove. I do not recommend this.

Torque for a 7/16 grade 8 bolt as recommended by GM is 60-65. I suggest using an ARP bolt kit for this application with a max torque of 70. The proper washer is also very important as a cheap one will deform & lose tension

Also do not use your balancer bolt to pull it on. There are proper tools for this application. You will likely ruin the bolt installing the dampener. Use an installation tool (essentially a stud with anti friction bearings) to be sure it is fully seated. NEVER pound the balancer on with a hammer as you will destroy the thrust bearing.

Hope this helps.

Originally posted by Lonnie Pavtis


Also do not use your balancer bolt to pull it on. There are proper tools for this application. You will likely ruin the bolt installing the dampener. Use an installation tool (essentially a stud with anti friction bearings) to be sure it is fully seated. NEVER pound the balancer on with a hammer as you will destroy the thrust bearing.

Hope this helps.

Ya i found out about not using the bolt to pull it on the hard way. Of course my buddy tells me after i broke the bolt off that he has the instalation tool.

As for pounding the hub on with a hammer, yes it is ruff on the thrust bearings. In my case i had no other options other than complete removal and disassembley of the enitre engine.

Thanks for the info Lonnie. :)

because of my really goofy setup down there I had to use a 7/16 by 6 inch stud from carquest and cut it down a little, (I actually needed like 5 1/4. Then I got a thick hardened fender washer and a big flanged nut, torqued to 80 foot pounds, didnt even use loc-tit. no problems. But I keyed my hub so I dont think spinning it would be a problem. espececally since I dont have a supercharger pulling on it, yet...